In U.S. Pat. No. 6,840,854 (Redekop) issued Jan. 11, 2005 of the present Assignees is disclosed a straw chopper and discharge apparatus for a combine harvester where a rotor carrying a series of flail blades is mounted for rotation about a horizontal axis at the rear of the combine harvester so that the blades sweep around a housing of the apparatus to carry the straw and optionally the chaff from an inlet opening of the housing to a discharge opening of the housing. A tail board is provided at the discharge opening with a series of fins so that the material discharged from the opening at high speed engages onto the board and the fins thereon for spreading. This patent in particular provides an improved arrangement of the blades for generating a higher velocity in the air and material being discharged.
In U.S. Pat. No. 6,939,221 (Redekop et al) issued Sep. 6, 2005 also of the present Assignees is disclosed an arrangement of the tail board which is formed in two separate side by side sections allowing independent adjustment of the two sections for enhanced spreading action.
The disclosure of each of the above two patents of the present assignees is incorporated herein by reference.
One of the primary requirements of residue management systems are that they evenly distribute residue over a combine's entire cutting width. Often a straw chopper or spreading mechanism will be able to cover the cutting width of the combine, however equally important is the consistency of the spread.
Variables such as a field's terrain, cutting height and wind direction alter the final placement of the residue. The straight cut headers mounted on the front end of today's harvesters are increasing in width due to the release of larger and more powerful combines. Currently the largest straight cut headers are 45 feet wide and some operators utilize a pick-up header to gather in a swath that is cut from a pass as wide as 60 feet. Most farmers want the spread width of the residue to match of width of cut, while maintaining an even distribution across the field, regardless of the external variables that may affect it.
Current methods to maintain even distribution with a wide spread are limited to a 40 feet width. Uncontrollable variables such as the wind speed and direction can significantly reduce both the spread width and an even distribution.
Even using the significant improvements set out in the above patents some difficulties remain with the existing technology in that the current device has a reduced ability to significantly propel straw from a chopper against a strong wind. The current machine technology will only spread 10-12 feet against a 10 mph wind.
Other arrangements have been proposed to improve spreading in such conditions but these commonly suffer from a high level of complexity and horsepower usage in order to spread 15 feet against the wind. For example the following publications provide some attempts to improve the spreading action albeit with little success:
US Application 2004/0127271 of Wolters assigned to CNH provides a chaff and straw spreading impeller with flow guide fingers and a top and rear surface to guide the residue.
EP 1187526/WO 00/78126 of Schrattenecker shows a chopper with fans mounted to each end of the chopper shaft with nozzles adjustable to position the air velocity at different locations on the outer fins.
U.S. Pat. No. 6,736,721 of Niermann issued in 2004 and assigned to Claas discloses a very complex design which spreads better against the wind. A chopper cuts the straw then discharges the residue into a spreader which has movable guides to alter the placement in the field. Negatives include even distribution and very high horsepower requirements which can be as much as three times the horsepower of the chopper itself.